A Rhizavidin Monomer with Nearly Multimeric Avidin‐Like Binding Stability Against Biotin Conjugates

Developing a monomeric form of an avidin‐like protein with highly stable biotin binding properties has been a major challenge in biotin‐avidin linking technology. Here we report a monomeric avidin‐like protein—enhanced monoavidin—with off‐rates almost comparable to those of multimeric avidin proteins against various biotin conjugates. Enhanced monoavidin (eMA) was developed from naturally dimeric rhizavidin by optimally maintaining protein rigidity during monomerization and additionally shielding the bound biotin by diverse engineering of the surface residues. eMA allowed the monovalent and nonperturbing labeling of head‐group‐biotinylated lipids in bilayer membranes. In addition, we fabricated an unprecedented 24‐meric avidin probe by fusing eMA to a multimeric cage protein. The 24‐meric avidin and eMA were utilized to demonstrate how artificial clustering of cell‐surface proteins greatly enhances the internalization rates of assembled proteins on live cells.     

Targeted exome sequencing resolves allelic and the genetic heterogeneity in the genetic diagnosis of nephronophthisis-related ciliopathy

Nephronophthisis-related ciliopathy (NPHP-RC) is a common genetic cause of end-stage renal failure during childhood and adolescence and exhibits an autosomal recessive pattern of inheritance. Genetic diagnosis is quite limited owing to genetic heterogeneity in NPHP-RC. We designed a novel approach involving the step-wise screening of Sanger sequencing and targeted exome sequencing for the genetic diagnosis of 55 patients with NPHP-RC. First, five NPHP-RC genes were analyzed by Sanger sequencing in phenotypically classified patients. Known pathogenic mutations were identified in 12 patients (21.8%); homozygous deletions of NPHP1 in 4 juvenile nephronophthisis patients, IQCB1/NPHP5 mutations in 3 Senior–Løken syndrome patients, a CEP290/NPHP6 mutation in 1 Joubert syndrome patient, and TMEM67/MKS3 mutations in 4 Joubert syndrome patients with liver involvement. In the remaining undiagnosed patients, we applied targeted exome sequencing of 34 ciliopathy-related genes to detect known pathogenic mutations in 7 (16.3%) of 43 patients. Another 18 likely damaging heterozygous variants were identified in 13 NPHP-RC genes in 18 patients. In this study, we report a variety of pathogenic and candidate mutations identified in 55 patients with NPHP-RC in Korea using a step-wise application of two genetic tests. These results support the clinical utility of targeted exome sequencing to resolve the issue of allelic and genetic heterogeneity in NPHP-RC.     

Direct numerical simulation of low Reynolds number flows in an open‐channel with sidewalls

A direct numerical simulation of low Reynolds number turbulent flows in an open‐channel with sidewalls is presented. Mean flow and turbulence structures are described and compared with both simulated and measured data available from the literature. The simulation results show that secondary flows are generated near the walls and free surface. In particular, at the upper corner of the channel, a small vortex called inner secondary flows is simulated. The results show that the inner secondary flows, counter‐rotating to outer secondary flows away from the sidewall, increase the shear velocity near the free surface. The secondary flows observed in turbulent open‐channel flows are related to the production of Reynolds shear stress. A quadrant analysis shows that sweeps and ejections are dominant in the regions where secondary flows rush in toward the wall and eject from the wall, respectively. A conditional quadrant analysis also reveals that the production of Reynolds shear stress and the secondary flow patterns are determined by the directional tendency of the dominant coherent structures. Copyright © 2009 John Wiley & Sons, Ltd.     

Interfacial tension reduction in PBT/PE/clay nanocomposite

We investigated the effect of organically modified nanoclay (organoclay) on immiscible polymer blends [polybutylene terephthalate (PBT)/polyethylene (PE)] with a special focus on the role of clay as a compatibilizer. When organoclay (Nanofil 919; Sud-Chemie, Inc.) is added to the blend, the clay first locates at the interface and then selectively locates in the PBT phase due to its affinity with PBT. This results in effective size reduction and narrowed size distribution of the dispersed phase. However, with a small amount of organoclay, it is observed that the clay locates at the interface regardless of its affinity for a specific component to minimize the chemical potential. The interfacial tension change of the blend with the addition of organoclay was quantitatively predicted from extensional force measurement. When the blend is subjected to an extension, the interfacial tension functions as a resistance against drop deformation. When we added organoclay to the blend, the extensional force was significantly reduced, which means that the contribution of the interfacial tension to the total force is reduced. For a 10/90 PBT/PE blend, the interfacial tension was reduced from 5.76 to 0.14 cN m⁻¹ when 1 wt% of organoclay was added. This interfacial tension reduction arises from the localization of the organoclay at the interface and its nonhomogeneous distribution along the interface, suppressing the coalescence between the droplets, which is a role of a compatibilizer. Conclusively, the immiscible polymer blends can be compatibilized with organoclay. The organoclay changes the blend morphology by interfacial tension reduction due to the localization of the organoclay at the interface and by the viscosity ratio change due to the selective localization by its affinity to a specific component in the blend.     

Synthesis of Cyclic N-Acyl Amidines by [3 + 2] Cycloaddition of N-Silyl Enamines and Activated Acyl Azides

In this study, we describe the synthesis of cyclic N-acyl amidines from readily available N-heteroarenes. The synthetic methodology utilized the versatile N-silyl enamine intermediates from the hydrosilylation of N-heteroarenes for the [3 + 2] cycloaddition reaction step. We evaluated various acyl azides and selected an electronically activated acyl azide, thereby achieving a reasonable yield of cyclic N-acyl amidines. We analyzed the relationship between the reactivity of each step and the electronic nature of substrates using in situ nuclear magnetic resonance spectroscopy. In addition, we demonstrated gram-scale synthesis using the proposed methodology.     

Production and characterization of an antibody specific for a novel protein serine/threonine kinase, MPK38, highly expressed in hematopoietic cells

We report an antibody that selectively recognizes MPK38, a new protein serine/threonine kinase closely related to the SNF1 serine/threonine kinase family. This antibody recognized a region of the N-terminal kinase catalytic domain and part of the remaining C-terminal portion and was sensitive enough to detect a 72-kDa recombinant MPK38 in insect cells by Western blotting. Immunoblot analysis showed that the recombinant MPK38 was expressed in a time-dependent manner and reached a maximum after 48 h postinfection. In addition, the immune complex kinase assay revealed that the recombinant and endogenous MPK38 protein autophosphorylated in vitro. Phosphoamino acid analysis of autophosphorylated MPK38 protein showed that the phosphorylation was exclusively on serine and threonine residues, suggesting that MPK38 is a protein serine/threonine kinase. Thus, this antibody could be helpful for elucidating the biological functions of MPK38 in the MPK38-expressing cells.     

Comparison of four scattering mechanisms in cyclotron resonance in InSb

Summary  Four scattering mechanisms are compared in the quantum limit cyclotron resonance inn-InSb on the basis of a many body theory introduced recently. In the quite low temperature region (T<70 K ) for the wavelength of the electromagnetic wave of 84 μ m, the electrons are scattered mostly by the ionized impurities, although the deformation potential phonon and the piezoelectric scattering are non-negligible. In the high temperature region (T>70 K ) the polar optical phonon scattering is found to be most dominant. It is also shown that the impurities give place to the phonons for the scattering mechanism above 70 K. On the other hand, at 20 K the ionized impurity scattering is dominant in the magnetic field region 0.2 T<B<2 T. This work has been supported by the Basis Science Research Institute Program, Korea Ministry of Education (Project No. BSRI-96-2405).     

Candidate gene polymorphisms for diabetes mellitus, cardiovascular disease and cancer are associated with longevity in Koreans

Long-lived people may have a unique genetic makeup that makes them more resistant than the general population to prevalent age-related diseases; however, not much is known about genes involved in the longevity. To identify susceptibility variants controlling longevity, we performed a high-throughput candidate gene study using 137 Koreans over 90 yr old and 213 young healthy Koreans. We evaluated 463 informative markers located in 176 candidate genes mostly for diabetes mellitus, cardiovascular disease and cancer under five genetic models. We estimated the odds ratios for each allele, genotype, haplotype, and gene-gene interaction using logistic regression analysis. Associations between 13 genes and longevity were detected at a P-value less than 0.01. Particularly, the rs671 (A) allele of the aldehyde dehydrogenase 2 family (mitochondrial) (ALDH2) gene was associated with longevity only in men (OR 2.11, P = 0.008). Four genes, proprotein convertase subtilisin/kexin type 1 (PCSK1, P = 0.008), epidermal growth factor receptor (EGFR, P = 0.003), paired box 4 (PAX4, P = 0.008), and V-yes-1 Yamaguchi sarcoma viral related oncogene homolog (LYN, P = 0.002) consistently yielded statistical evidence for association with longevity. The findings of the current study may provide a starting point for future studies to unravel genetic factors controlling longevity in Koreans.     

Interfacial localization of nanoclay particles in oil-in-water emulsions and its reflection in interfacial moduli

The localization of nanoclay particles dispersed in the oil phase of a model oil-in-water emulsion depends on the wetting property of layered nanoparticles. Investigation at a single droplet interface shows that nanoclay is located at different interfacial regions depending on the hydrophilic property of the nanoclay surface. Hydrophobic nanoclays do not present Pickering phenomena at the interface and hardly form an interfacial layer. Hydrophilic nanoclay particles quickly move to the interface and form a Pickering interface with a high interfacial shear modulus. With surfactant, poor hydrophilic nanoclays can be located at the interface due to improvement of the wetting behavior caused by the surfactants dissolved in the aqueous continuous phase. With ionic molecules changing the wetting behavior of particles, the interfacial localization of nanoclays can be controlled and improve the mechanical property of emulsion.